volume control,stepped attenuator


	Higher demands Resistors	Volume control The ultimate

	Higher demands The pursuit for better sound quality goes steadily on and as an example, a new CD standard of perhaps 24bit/96 kHz would be a welcome improvement. As resolution, transparency etc. reach higher levels produced through our equipment, so do the demands increase for better passive components such as cables, contacts, volume controls, capacitors, resistors etc. Their own degrading sonic fingerprints become more audible in our refined systems. Under AC-conditions these components have undesirable reactive affects which distort the audio signal. Resistors TOP Resistors are neither technically nor audibly perfect. Some important measurable characteristics are: non-linearity, induction, capacitance and signal/noise ratios. One resistor type is wound like a coil and of course has high induction whereas carbon resistors in general have high distortion levels. Other resistors are relatively high magnetic causing remanence during AC- operation and others have high capacitance’s. The audible effects are variable and also dependent of the quality of the stereo system in general. In any case, some resistors are so bad (both audibly and technical data ) that they can not be used in an audio system. A resistor’s non-linearity is the change of resistance value caused by a change of the voltage, i.e. a typical music signal. Various resistor types increase in resistance and others decrease during similar conditions. This phenomena results in dynamic distortion, either as compression or expansion depending upon type and coupling. Resistors also produce distortion products which usually are measured in dB of the 3’rd harmonic level relative to the input signal. A typical value for a 10 kohm SMD chip-resistor is in the order of only -60 dB! ( See various manufacturers own data specs.) In comparison, a 1/4 W metal film resistor of the same resistance value displays a distortion level of approximately -115 dB. This is an enormous difference which definitely is audible! Volume control TOP A volume control is in principle a voltage divider consisting of a series and a ground resistor. The relationship between the resistance values can be changed so as to set the required signal level. There are two main groups : 1) stepped attenuators using fixed resistors and 2) potentiometers. The resistance path of a potentiometer usually consists of a thin carbon film. These have poor linearity, low bandwidth and a low S/N ratio. Another type of potentiometer uses a resistance wire which is wound as a coil. This type has also a high level of induction which together with it’s other reactive characteristics causes a fantastic sonic imprint. It is great for destroying the music signal and can be used effectively for masking other defects of a bad design. Stepped attenuators are more commonly used in expensive hi-end equipment. High quality fixed resistors are coupled in series where the signal output is taken variably along the chain of resistors. Compared to potentiometers, stepped volume controls with fixed resistors have better technical data and higher sonic qualities. However, one problem with this type of attenuator is that distortion is produced in each individual resistor and some of these products are added along the chain. With 24 resistors, all in series with the signal path, this concept is not an optimal solution. There are methods to bypass this disadvantage but with traditional two-decked attenuators the input impedance will vary with the volume setting. The ultimate TOP The best stepped attenuator is one that never has more than one resistor in the signal path and which uses separate voltage dividing networks for every volume setting. This construction is much more complex, totaling 1 signal and 1 ground resistor at 24 positions and 2 channels = 96 resistors (4 are 0 ohm) but the advantage is a much reduced signal path (1/24) for every volume level. The long chain of series resistors is eliminated, various distortion products effectively reduced and constant input impedances can be tailored. With the resistors used in our volume controls, 3'rd harmonic distortion is kept at exceptionally low levels. Listening tests have proven the theories and this construction, used in Audiolive's other products, ought to be an ultimate solution to the problems of passive and digital volume controls. Only one high-quality resistor in the signal path and using the Swiss made precision attenuator with gold contacts for low contact resistance and longtime durability.

	TOP Audiolive S-14233 Skogås Sweden Tel.+46- (0)8- 7715437 http://home.swipnet.se/~w-60838 E-Mail audiolive@swipnet.se Updated 2000-03-04

The pursuit for better sound quality goes steadily on and as an example, a new CD standard of perhaps 24bit/96 kHz would be a welcome improvement. As resolution, transparency etc. reach higher levels produced through our equipment, so do the demands increase for better passive components such as cables, contacts, volume controls, capacitors, resistors etc. Their own degrading sonic fingerprints become more audible in our refined systems. Under AC-conditions these components have undesirable reactive affects which distort the audio signal.

Resistors TOP

Resistors are neither technically nor audibly perfect. Some important measurable characteristics are: non-linearity, induction, capacitance and signal/noise ratios. One resistor type is wound like a coil and of course has high induction whereas carbon resistors in general have high distortion levels. Other resistors are relatively high magnetic causing remanence during AC- operation and others have high capacitance’s. The audible effects are variable and also dependent of the quality of the stereo system in general. In any case, some resistors are so bad (both audibly and technical
data ) that they can not be used in an audio system.
A resistor’s non-linearity is the change of resistance value caused by a change of the voltage, i.e. a typical music signal. Various resistor types increase in resistance and others decrease during similar conditions. This phenomena results in dynamic distortion, either as compression or expansion depending upon type and coupling. Resistors also produce distortion products which usually are measured in dB of the 3’rd harmonic level relative to the input signal. A typical value for a 10 kohm SMD chip-resistor is in the order of only -60 dB! ( See various manufacturers own data specs.) In comparison, a 1/4 W metal film resistor of the same resistance value displays a distortion level of approximately -115 dB. This is an enormous difference which definitely is audible!

Volume control TOP

A volume control is in principle a voltage divider consisting of a series and a ground resistor. The relationship between the resistance values can be changed so as to set the required signal level. There are two main groups : 1) stepped attenuators using fixed resistors and 2) potentiometers. The resistance path of a potentiometer usually consists of a thin carbon film. These have poor linearity, low bandwidth and a low S/N ratio. Another type of potentiometer uses a resistance wire which is wound as a coil. This type has also a high level of induction which together with it’s other reactive characteristics causes a fantastic sonic imprint. It is great for destroying the music signal and can be used effectively for masking other defects of a bad design.
Stepped attenuators are more commonly used in expensive hi-end equipment. High quality fixed resistors are coupled in series where the signal output is taken variably along the chain of resistors. Compared to potentiometers, stepped volume controls with fixed resistors have better technical data and higher sonic qualities. However, one problem with this type of attenuator is that distortion is produced in each individual resistor and some of these products are added along the chain. With 24 resistors, all in series with the signal path, this concept is not an optimal solution. There are methods to bypass this disadvantage but with traditional two-decked attenuators the input impedance will vary with the volume setting.

The ultimate TOP

The best stepped attenuator is one that never has more than one resistor in the signal path and which uses separate voltage dividing networks for every volume setting. This construction is much more complex, totaling 1 signal and 1 ground resistor at 24 positions and 2 channels = 96 resistors (4 are 0 ohm) but the advantage is a much reduced signal path (1/24) for every volume level. The long chain of series resistors is eliminated, various distortion products effectively reduced and constant input impedances can be tailored. With the resistors used in our volume controls, 3'rd harmonic distortion is kept at exceptionally low levels. Listening tests have proven the theories and this construction, used in Audiolive's other products, ought to be an ultimate solution to the problems of passive and digital volume controls. Only one high-quality resistor in the signal path and using the Swiss made precision attenuator with gold contacts for low contact resistance and longtime durability.

TOP

Audiolive
S-14233 Skogås
Sweden
Tel.+46- (0)8- 7715437

http://home.swipnet.se/~w-60838
E-Mail audiolive@swipnet.se

Updated 2000-03-04